Multiservice switches used, for example, by communications providers in wide area networks typically provide a number of different interfaces for incoming and outgoing communications traffic to the core switching fabric in order to accommodate customer needs. These interfaces can range, for example, from high rate optical trunking ports to lower rate electrical interfaces. In general, the different interfaces are provided through service specific equipment grouped together on what are termed “service shelves”, where the service shelves then couple to the switching core. A typical service shelf will include the physical layer interface which couples to higher layer service cards (e.g. layer 2 or 3 for ATM or IP) and then to the switching core. Failure protection of equipment utilized in multiservice switches usually in the form of redundant circuit paths is also extremely important in order to provide the type of reliability that is necessary for these switches. That is, the ability to detect faults in a packet switching system and restore service quickly is an important issue in overall availability to the customer. Extra service cards (or protection cards) and even redundant switching cores are often provided within a service shelf to allow for the required fault protection.
In prior art multiservice switches of the type described above, in order to perform maintenance on a portion of the switch, e.g. replacing a service card, it was required that all data flows in the switch be transitioned from one core to the other. This transition is typically accomplished in a relatively uncontrolled manner causing cell drops or other Quality of Service (QoS) disruptions to user data. Moreover, prior art switchover methodologies required that the redundant switching cores be aligned in time to some small percentage of a packet period or multiples thereof, thereby further complicating the equipment design and switchover task. A need therefore exists for a simplified switchover methodology without cell loss in a multiservice switch that does not require synchronization of the redundant cores and that may be utilized to control portions of the overall data flow.